Lockable enclosures are used in many indoor and outdoor environments to restrict access to various items by providing the enclosure with a lockable door, lid, drawer, or other such barrier. The bather can include a locking mechanism, such as, for example, a combination lock, padlock, set of pushbuttons, or key operated latch, to limit access to the contents of the enclosure to one or more authorized users. Some applications may require secure storage of one or more smaller items, such as keys, credit cards, or documents, for which restricted access by a limited number of authorized individuals is desirable. One example of such an enclosure is a key safe, which is affixed to an entry door (e.g., shackled around the doorknob) of a building for secure retention of an authorized key for the entry door. The key safe may employ, for example, a pushbutton or combination dial locking mechanism, such that authorized users informed of the unlocking combination may open the key safe to access the door key for entry into the building.
Mechanical pushbutton combination locks have been provided, for example, to allow for a pushbutton locking arrangement without requiring an electrical power source to maintain accessibility to the locking mechanism (i.e., without risk associated with power outages or battery depletion). Conventional mechanical pushbutton combination locks employ a series of buttons each operable between two different states or conditions—a depressed or selected condition and a non-pressed or unselected condition. When the correct buttons (and only the correct buttons) have been depressed, a lock member associated with the locking arrangement becomes movable from the locked condition to the unlocked condition. When at least one of the incorrect buttons has been depressed or when at least one of the correct buttons has not been depressed, the lock member remains blocked from movement to the unlocked condition. In this type of arrangement, the number of potential combination codes is limited by the fact that the combination codes are not sequence-dependent, and that each button has only two states—a selected condition and a non-selected condition.